Like Rich advises, you should try the Blade forum <http://www.bladeforums.com>.
More specific to your question, the only magic blade I am aware of was the Xcalabar which was procured from some lady in a lake some years before I joined the Navy. You may want to contact an Arthurian web site for detail.
Today we are lucky enough to have a wide variety of blade types at our disposal, some practical, some art form and practical, and some strictly art at the highest level. If you are looking for a combat folder, or a practical pocket knife that could be effectively used for self defense you will get all the advice you want from the troops over at the Blade forum, but price should not be an issue if you are looking for quality, there are many commercial sources such as have mentioned. Prices range from 80$ to $250. My only suggestion is to select a liner blade lock system as the back lock systems have been known to close on fingers in edged classes - makes for a real bad day.